This invention relates to a tool for holding a rigid element, such as a nail set, during the application of a hammer blow thereto and, more particularly, to such a tool which effectively prevents overdriving of the element under normal conditions and shields the workpiece.
The performance of finished carpentry work involves the sinking of narrow-head finishing nails beneath the surface of wood or wood-like workpieces. After a finished nail is driven into the workpiece, the resulting hole therein above the nail head is covered with a suitable filler to hide the nail hole and nail in the finished product. It is of the utmost importance that the nail is not overdriven and the workpiece struck by the hammer and thereby damaged. Accordingly, the driving of the finished nail by experienced carpenters is customarily only performed in two steps. First, the nail is only partially driven into the workpiece to a depth such that the head, and sometimes a portion of the shank, protrudes above the surface. The second step involves driving the nail beneath the surface, i.e., "setting" the nail, with a nail set punch.
This technique of setting nails suffers from more than a few disadvantages when only a conventional nail set punch and hammer are employed. First, as the nail head comes closer and closer to the surface of the workpiece, the danger of overdriving the nail increases. Accordingly, as the nail head approaches the surface, prudent carpenters decrease the force of each hammer blow, which thereby increases the number of strokes needed to drive the nail within the desired distance and adds to the time for completing the work. Next, due to the narrow end of the nail set having a diameter substantially the same as that of the nail, inattention often results in the nail set slipping off the head of the nail during or immediately before the punch is struck by the hammer. When this occurs, the workpiece is damaged by the nail set being driven into the workpiece alongside the nail. This slippage problem is aggravated when the location or configuration of the workpiece is such that it is difficult to coaxially align the nail set and the nail. Likewise, due to workpiece location, it is many times difficult to hold a nail in the desired location before application of the initial blow. Generally, because of these problems, the setting of nails during finish work has been a fatiguing and slow work process.
A number of devices have been proposed to resolve some of the difficulties noted above. Nail holders are shown in U.S. Pat. No. 3,060,442 of Tomek and U.S. Pat. No. 2,871,480 of Pezza et al. In Tomek, a headed nail is held between two resilient, flexible arms. When a nail is driven too far, the head of the nail acts against chamfered edges of the arms which are thereby separated to release the nail. However, the arms, while being somewhat resilient, are not intended to be struck by the hammer except by accident, and if struck, may cause damage to the workpiece. A further disadvantage of the Tomek holder is due to the resilient arms being attached to an elongate, substantially rigid body, for the rigidity of the body substantially prevents use of the nail holder in many inaccessible locations. In tne patent of Pezza et al, a punch is provided with a mechanism at one end thereof for holding the nail against the end of the punch whereby the punch itself functions as a holder. Again, however, a danger remains of driving the enlarged end of the punch into the workpiece. Accordingly, after the nail has been only partially driven into the workpiece, the hold on the nail is released and the punch is used in a conventional fashion.
A nail driving shield is shown in U.S. Pat. No. 3,338,279 of Kruttschnitt for preventing overdriving of the nail. The shield, however, is rigid, and if struck by the hammer with sufficient force, will indent the surface of the workpiece, particularly if the surface is curved. The disc-like shape and rigidity of the shield also prevents its effective use in corners or the like. A rigid shield especially designed for nailing tongue and groove flooring, but otherwise similar to the shield of Kruttschnitt, is shown in U.S. Pat. No. 3,010,496 of Bruce.
An attempted solution to the slippage problem is provided by a nail setting tool shown in U.S. Pat. No. 1,838,462 of Stanford, in which a punch housing fitted over the nail head maintains proper coaxial alignment. However, as with Pezza et al, no provision is made to prevent driving the punch housing into the workpiece along with the punch.